Solar Panel choices: SunPower E20 vs Solaria PowerXT vs Hanwha (QCell)

What do PVGIS/PVWatts give at your location? I guess around 900kWh/kWpeak. What is the FIT? In Germany we have FIT of 12.08 Eurocent per kWh (for size up to 10kWp roof mounted residential) garanteed for the year of connection + 20 full years. The owner has to register a business with the taxman but he therefore buys without VAT. And he has to declare his profits in his tax declaration. Installers are very agreesively pushing battery storage here (because of their margin - otherwise margins are slim). But the best storage of them all is the grid itself. So here it's economy of scale vs. measly FIT. The forum wizards on the German forum came to the conclusion: fill up your good roofs up to 10kWp, find a good planner/installer - and you'll make a small profit (repay time 12+- years).
Installation costs recently have come down (cheaper modules the main reason). There have been 10kWp systems at under 1000 Euro per kWp lately.

FIT is feed in tariff --rate government pay you for power sold back to them for 20 years
I just checked it has now dropped to around 0.05gbp
so getting even worse
this website gives all historical and current FIT rates

Solar Panel Grants 2024 | Eligibility & Savings Explained

https://www.theecoexperts.co.uk/solar-panels/government-grants-free

The latest UK government grants and funding schemes to help pay for solar panels on your home - start saving on your energy bills today

could be no FIT by time I get round to build --which will be next year
what with brexit and SNP independance --who knows
I will revisit solar PV again closer to time and see how it stacks up

Ok
I have gone on to goverment site and done calculation ona 4kw system
the results are worse than i thought --FIT has dropped again 0.036gbp
i would attach the PDF file showing their results--but can see no way of attaching file to this forum


basically it will take 24 years to pay back
a non starter --25years to make 1250gbp

https://www.expertsure.com/uk/home/t...el-calculator/ is a calculator. I have no idea how accurate it is (and the assumptions making that calculations). Play around with the numbers. If it's a new construction try to fill the unshaded south facing roof plane with a slope of 30 degrees+. Try to find an install under 1.1 pounds per Wp.
A sample calculation: Edinburgh postcode, 8kWp, 9900 pounds, 50% export : (16840/9900+1)^0.05=1.05. 5% annually aren't much but at least it's profitable. Pay back time ln2/ln1.05=14 years.
Once FIT is gone it most likely will be even worse.

so at that rate its not worth doing , which is what i,m thinking --will see what is on offer closer to the time .
roof angle will be more like 40-45degrees ,but 8kw array is a very large area to fit on a two level house roof --fine if big bungalow cos roof area will be larger
why does it give best results at 40,when latitude in 54?
my postcode dg8 6ah

Kind of what I was thinking.

I doubt the probability of PV ever being cost effective in your climate will ever be that high.

I'd respectfully suggest putting more thought and effort into conservation and some unobtrusive passive solar via widow placement, that sort of thing.

I still think solar thermal has a chance for heating house + dhw ,with large enough well insulated tank --but again till I get house design finished +thermal load is known it is hard to say how big a tank- my guess at this stage is 12000litres -- 2mx2mx3 m high
been doing some plotting and asking grp resin suppliers questions --would seem easiest way to make a tank that will last 50 years is grp lined
build it from concrete blocks 12" thick and lay grp directly onto inside of block work -plenty of resins that will take 100c for ever +although it will be a pain to do-i will have to go inside it to lay it up
I am well versed in making things in GRP
.--then surround block work with insulation
cost it all then compare to cost air source heat pump system

Solar thermal will only have a chance in your solar climate and then only a slim one. To have any chance at cost effectiveness, you'll need to first give up the idea of evac. tube collectors. They simply cost too much. Before that however, you will also need to first reduce your hot water load through lower use temps. and lower draw, as well as effective line insulation.

As you get more educated and move forward, my guess is you'll modify or abandon some preconceived notions about what works, what's achievable, what's practical and what's cost effective.

For starters you will never see anything cost effective for your applications or climate that uses solar thermal and will have an operating or even a needed design temp. of 100 C.

Not meant as a wet blanket, but I've been where you're at in the solar journey. Take it FWIW.

Respectfully,

Before you build, evaluate if you have enough sun to generate enough heat , then check this DIY system out.

I have had 2 x20 thermomax evac tubes for last 20 years and know I how much sun i get --the only problem as i see it is storing it long enough+ stopping stagnation of panels
for it to work I need my tank to get to 80c+ by end of summer ,which is why I,m using 100c as absolute max temp for tank lining+ smaller buffer tank so when in winter i can only get 30c from panels once main tank has reached lower temp limit
it will go direct to underfloor first and then to big tank if any surplus above min tank temp
my underfloor in this house works happily on 30c water temp to get a room temp of 23c.-- --
I take what you say ,but still maintain it will all be decided by the heat load of the new house design -my present house is about 15 kw,so if i can drop it to 5kw or less then it will be possible .
as it will also be a lot easier to keep rooms at target temps due to insulation of new house
viability will then be decided on initial cost and the savings in running costs
I take on what you say about costing of panels but from my talks with panel makers evac panels will give close to twice the output that flat ones do in UK
I understand why you go for them in your climate . keeping panels from shutting off for half the day because the tank is too hot is where I expect to gain the edge.
I go back to simple physics --1000litres at 40c = 500litres at 80c ,as far as energy is concerned,which is where my concrete thermal mass storage around the tank comes in
it will keep tank temp down ,so allowing it to keep on collecting energy.I know my old simple controller worked quite happily with a 6c difference between collector and tank .
I also used a thermo blender on domestic hot water to 45c so I was not using water at 70c c and then adding cold at the sink
my next part of the project is too do some work on the actual heat exchanger I will use in the big tank ,as maximium surface area is the goal and with a large tank 2mx2m footprint
I am not going to be short of space --possibly a couple of cast aluminium radiators in parallel.or maybe multliple car radiators--certainly think simple copper tubing can be improved on
Yes i,m pretty determined to do this --but nothing will be made until house design and heat load is known
If you can build a house now with virtual zero energy requirement ,then it must be possible to use solar thermal for both dhw + space heating
there is a nagging thing at back of my mind which says if house does only require 5kw ,then an inline electric 5kw boiler which costs only 600gbp
coupled direct to underfloor is probably the cheapest way by far !!!!.
for you guys where solar PV works then it could also be a winner on the right house,or just use 3kw imersion elements 20gbp each in thermal store
heat pump or solar will cost thousands to do --so it would depend how long I live what would be cheapest overall in long run LOL
yes I,m in of need Psychiatric help .LOL

John:

Good luck. I can only offer a respectful suggestion meant in the best possible way that with education being priceless, and paper mistakes being easier and cheaper to correct than construction mistakes, you learn as much about why some of your notions may not be the best long term ways to go before you commit to them. Whatever you choose , I wish you the best,

J.P.M.

Guess I am late to the party. FWIW Solaria is now at 87% on their 25 year warranty.